http://www.ebay.com/itm/NOS-DUCATI-MH90 ... fd&vxp=mtr
or
http://www.ebay.co.uk/itm/New-Genuine-D ... 27cdfbbcf9
Regulator/rectifiers are a standard problem on older Ducatis. There are several aftermarket replacements. Often used is the Electrosport/Electrex RR51.
"Tickover" means "idle".

G.